The present invention relates to a magnetic tape cartridge. More particularly, the present invention relates to improvements in a magnetic tape cartridge, in the cartridge case of which a single reel is rotatably accommodated and a magnetic tape is wound around the reel.
There is provided a conventional magnetic tape cartridge used as a recording medium for an external memory of a computer, in which a magnetic tape is wound around a single reel. This magnetic tape cartridge is used for storing data for the computer. Therefore, important data is stored in the magnetic tape cartridge. Accordingly, this magnetic tape cartridge is composed so that problems such as tape jamming can not be caused in the magnetic tape cartridge and so that the magnetic tape can not be carelessly drawn out from the magnetic tape cartridge.
FIG. 2 is a view showing a conventional example of the magnetic tape cartridge.
This magnetic tape cartridge 1 is composed as follows. In the magnetic tape cartridge 1, there is provided a single reel 3 composed of an upper reel 4 and a lower reel 5 which are combined with each other by means of ultrasonic welding. Around the single reel 3, a magnetic tape 20 is wound. There is provided a cartridge case 2 composed of an upper case 2a and a lower case 2b which are fastened to each other with screws 19. In this cartridge case 2, the reel 3 is rotatably accommodated.
The upper reel 4 is formed by molding in such a manner that a cylindrical reel hub 42 having a bottom, around the outer circumference of which the magnetic tape 20 is wound, and a flange portion 43 protruding from the outer circumference of the upper edge of the reel hub 42 in the radial direction are integrally molded. On an outer surface of the bottom portion of the reel hub 42, there are provided engaging teeth which are used as an engaging means for driving the reel. At an outer circumferential edge of the flange portion 43, there is provided a braking gear 43a which engages with reel locks 50, 51 when the rotation of the reel is restricted in the case of not using the magnetic tape cartridge. In this connection, a recess portion of the reel hub 42 having the bottom portion is open to the upside.
The lower reel 5 is formed into a disk-shape, at the center of which an opening 5a is formed into which the outer surface of the bottom portion of the reel hub 42 is inserted. The lower reel 5 is integrated with the upper reel 4 by means of ultrasonic welding.
When the reel 3 composed of the upper reel 4 and the lower reel 5 by integral ultrasonic welding is incorporated into the cartridge case 2, a bearing 6 is press-fitted into the recess having the bottom of the reel hub 42, and further a spring plug 7 is press-fitted into a hole at the center of the bearing 6. A reel spring 8 attached to the spring plug 7 pushes the reel 3 downward and holds it rotatably.
In order to prevent the reel 3 from rotating carelessly when the cartridge is not used, the braking gear 43a is engaged with the reel locks 50, 51 by the action of pushing forces generated by the torsion springs 12. When the magnetic tape cartridge 1 is not used, under the condition that the magnetic tape 20 is completely wound around the reel 3, a leader tape 21 attached to an end of the magnetic tape 20 is engaged with a front end portion of the hook 18 which is incorporated along the side of the cartridge, wherein the leader tape 21 is a means for introducing the magnetic tape 20 into a predetermined tape running passage in the recording and playback device in which the magnetic tape cartridge 1 is used.
On the side walls of the upper case 2a and the lower case 2b which compose the cartridge case 2, there are provided cutout portions 24a, 24b which are formed into an opening 24 from which the magnetic tape 20 is drawn out. At one corner of the opening 24 for drawing out the magnetic tape, there is provided a lid 30 capable of being opened and closed in the direction of the plane of the cartridge around a support shaft 14 and a support shaft boss portion 14a, wherein the lid 30 is appropriately pushed by a torsion spring 15. In order to prevent the rotation of the lid 30 when the cartridge is not used, the lid 30 is engaged with a lid lock 40 which is appropriately pushed by the lid lock spring 16. On the side opposed to the lid 30, there is provided a writing protect piece 17.
When the above magnetic tape cartridge 1 is set in a corresponding external memory of a recording and playback device, a driving means provided in the recording and playback device is engaged with the engaging teeth of the reel 3 exposed in the opening 2c at the center of the lower case 2b. At the same time, the lid 30 is opened by a tape drawing mechanism provided in the recording and playback device. Therefore, the leader tape 21 is drawn into a predetermined position in the tape running passage. In this way, data can be read from and written on the magnetic tape 20.
In this connection, a cartridge guide member (not shown in the drawing) provided in the recording and playback device relatively strongly comes into contact with one portion of the side of the cartridge case 2, that is, a cartridge guide member provided in the recording and playback device relatively strongly comes into contact with an outer circumferential surface of the side wall 2d close to the support shaft boss 14a of the lower case 2b. While the cartridge guide member is coming into contact with this outer circumferential surface of the side wall 2d, the magnetic tape cartridge 1 is guided and it can be set in and taken out from the recording and playback device.
Due to the fluctuation of production of the deck of the recording and playback device and the magnetic tape cartridge 1, a frictional force is increased which is generated between the side wall 2d of the lower case 2b made of polycarbonate containing glass fiber, the sliding property of which is low, and the guide member of the cartridge. Accordingly, there is a possibility that the magnetic tape cartridge 1 can not be ejected smoothly.
When the magnetic tape cartridge 1 is repeatedly inserted into the deck of the external memory of the computer as indicated by arrow A in FIG. 2 or when the magnetic tape cartridge 1 is repeatedly drawn out from the deck of the external memory of the computer as indicated by arrow B, scratches D to deteriorate the appearance are caused in a portion between a pair of system discriminating ribs 80, 81, which are arranged at a predetermined interval, on the side wall 2d with which the guide member comes into contact.